Quantifying The Effects Of Nitrogen On Dry Matter Production And Partitioning Of Standard Cut Chrysanthemum Morifolium. 'Shenma' In Solar Greenhouse

Dry matter and dry matter partitioning is the base of external quality formation of ornamental plants. Nitrogen is the important nutrient affecting dry matter production and dry matter partitioning of plants. The aim of this study is to quantitatively investigate the effects of nitrogen on dry matter partitioning of solar greenhouse standard cut chrysanthemum. Experiments of standard cut chrysanthemum (Chrysanthemum morifolium. 'Shenma') with different planting dates and different levels of nitrogen application rates were conducted in a solar greenhouse in Beijing during October, 2005 and July, 2006. The integrated photo-thermal index, the product of thermal effectiveness, PAR and day length (PTEP), was used to describe the changes of the leaf area index (LAI) and the partitioning indices of leaf, stem and flower with development stages. Effects of the accumulated leaf nitrogen content at bud showing stage on the dynamics of the maximal photosynthesis rate, the leaf area index and the partitioning indices of leaf, stem and flower were quantified based on experimental data. Based on these quantitative relationships, a model for predicting the effects of nitrogen on dry matter production and partitioning of standard cut chrysanthemum in solar greenhouse was developed. Independent experimental data were used to validate the model. The results showed that the model developed in this study can predict the leaf area index, total dry weight, dry weight of stem, leaf and flower of plants of the solar greenhouse standard cut chrysanthemum.(1) Quantifying the effects of nitrogen on the maximal total photosynthesis rate, leaf area index and dry matter production of standard cut Chrysanthemum 'Shenma' in solar greenhouse .The aim of the study was to quantitatively investigate the effects of nitrogen on dry matter production of solar greenhouse standard cut chrysanthemum. PTEP was used to described the change of the leaf area index with development stages. Effects of accumulated leaf nitrogen content on the dynamics of the leaf area index and the maximal total photosynthesis rate were quantified. And integrated the crop growth model, a model for predicting the effects of nitrogen on dry matter production of standard cut chrysanthemum in solar greenhouse was developed. Independent experimental data were used to validate the model. The result showed that the relation between the maximal photosynthesis rate and accumulated leaf nitrogen content were fond as follows:P_g,max =35×(1-EXP(-47×(N_a-0.43)/37)) R²=0.86 SE=1.52kg CO₂·hm^-2·h^-1The relation between LAI and PTEP and the maximum of leaf area index (LAW) and the increasing rate of LAI (a) and the accumulated leaf nitrogen content (N_L) at bud showing stage of standard cut chrysanthemum were described as follows: LAI=LAI_max×(1-EXP(-a×(PTEP-PTEP₀)/LAI_max)) LAI_max=13.86×(1-EXP(-9.18×N_L/13.86)) R²=0.99 SE=0.053a=0.167×(1-EXP(-0.10×N_L/0.167)) R²=0.95 SE=0.0037When using the above formulas to predict leaf area index and total dry weight, the coefficient of determination (R²) between the simulated and measured leaf area index and total dry weight of the standard cut chrysanthemum plants based on the 1:1 line were0.91, 0.93,respectively, the relative prediction error (RE) between the simulated and measured leaf area index and total dry weight of the standard cut chrysanthemum plants were 6.46%, 9.8%, respectively.(2) Quantifying analysis between the effects of nitrogen on dry matter partitioning of cut chrysanthemum. The aim of this study is to quantitatively investigate the effects of nitrogen on dry matter partitioning of solar greenhouse standard cut chrysanthemum. PTEP was used to describe the changes of the partitioning indices of leaf, stem and flower with development stages. Effects of the accumulated leaf nitrogen content at bud showing stage on the dynamics of the partitioning indices of leaf, stem and flower were quantified based on experimental data. Based on these quantitative relationships, a model for predicting the effects of nitrogen on dry matter partitioning of standard cut chrysanthemum in solar greenhouse was developed. Independent experimental data were used to validate the model. The results show that there were no effect of nitrogen on partitioning indices of shoot, stem, leaf and flower of cut chrysanthemum and obvious effect of nitrogen on partitioning indices of leaf stem and flower. The relation between the partitioning indices of shoot, stem, leaf and flower of cut chrysanthemum and PTEP after transplanting were described as follows:PISH=0.919×(1-EXP(-0.023×PTEP/0.919)) R²=0.90 SE=0.011PIST=PIST_min+(PIST_max-PIST_min)/(1+EXP(-b×(PTEP-PTEP_a)))PIL=PIL_min+(PIL_max-PIL_min)/(1+EXP(c×(PTEP-PTEP_a))) PIF=d×PTEP_bThe increasing rate of the partitioning index of stem (b) and the decreasing rate of the partitioning index of leaf (c) increased, and the increasing rate of the partitioning index of flower (d) decreased; The relation between the increasing rate of the partitioning index of stem (PIST) (b) and the maximum value of PIST (PIST_max) and the decreasing rate of the partitioning index of leaf (PIL) (c) and the minimum value of PIL (PIL_min) and the increasing rate of the partitioning index of flower (PIF) (d) and the accumulated leaf nitrogen content at bud showing stage can be described by the funcations as follows:PIST_max=1.687/(1+EXP(0.694×N_L/1.687)) R²=0.99 SE=0.0017b=0.141/(1+EXP(-0.058×N_L/0.141)) R²=0.95 SE=0.0011PIL_min=0.559×(1-EXP(-0.41×N_L/0.559)) R²=0.99 SE=0.0029c=0.116/(1 +EXP(0.057×N_L/0.116)) R²=0.96 SE=0.0009d=0.00078^*(1-exp(-0.00095×N_L/0.000078)) R²=0.93 SE=0.000017When using the above formulas to predict the dry weight of stem, leaf, flower of the standard cut chrysanthemum plants, the coefficient of determination (R²) between the simulated and measured dry weight of stem, leaf, flower of the standard cut chrysanthemum plants based on the 1:1 line were 0.96, 0.97, 0.94, respectively; and the relative prediction error (RE) between the simulated and measured dry weight of stem, leaf, flower of the standard cut chrysanthemum plants were 8.26%, 5.76%, 3.70%, respectively.The model developed in this study can predict LAI, total dry weight and dry weight of stem, leaf and flower of the standard cut chrysanthemum plants grown in the solar greenhouse satisfactorily using planting date, density, start date of the short day, air temperature, radiation, day length, and the N available in the soil during the experimental season as input, hence, can be used for optimization nitrogen management for solar greenhouse standard cut chrysanthemum production.